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SubjectRe: [PATCH v6 2/2] tty: add rpmsg driver
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Hi Arnaud,

Le 04/09/2019 à 15:09, Arnaud Pouliquen a écrit :
> This driver exposes a standard tty interface on top of the rpmsg
> framework through a rpmsg service.
>
> This driver supports multi-instances, offering a /dev/ttyRPMSGx entry
> per rpmsg endpoint.
>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
> Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
> ---
> Documentation/serial/tty_rpmsg.rst | 45 ++++
> drivers/tty/Kconfig | 9 +
> drivers/tty/Makefile | 1 +
> drivers/tty/rpmsg_tty.c | 418 +++++++++++++++++++++++++++++++++++++
> 4 files changed, 473 insertions(+)
> create mode 100644 Documentation/serial/tty_rpmsg.rst
> create mode 100644 drivers/tty/rpmsg_tty.c
>
> diff --git a/Documentation/serial/tty_rpmsg.rst b/Documentation/serial/tty_rpmsg.rst
> new file mode 100644
> index 000000000000..fc1d3fba73c5
> --- /dev/null
> +++ b/Documentation/serial/tty_rpmsg.rst
> @@ -0,0 +1,45 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=============
> +The rpmsg TTY
> +=============
> +
> +The rpmsg tty driver implements serial communication on the RPMsg bus to makes possible for user-space programs to send and receive rpmsg messages as a standard tty protocol.
> +
> +The remote processor can instantiate a new tty by requesting:
> +- a "rpmsg-tty-raw" RPMsg service, for TTY raw data support without flow control
> +- a "rpmsg-tty-ctrl" RPMSg service, for TTY support with flow control.
> +
> +Information related to the RPMsg and associated tty device is available in
> +/sys/bus/rpmsg/devices/.
> +
> +RPMsg TTY without control
> +---------------------
> +
> +The default end point associated with the "rpmsg-tty-raw" service is directly
> +used for data exchange. No flow control is available.
> +
> +To be compliant with this driver, the remote firmware must create its data end point associated with the "rpmsg-tty-raw" service.
> +
> +RPMsg TTY with control
> +---------------------
> +
> +The default end point associated with the "rpmsg-tty-ctrl" service is reserved for
> +the control. A second endpoint must be created for data exchange.
> +
> +The control channel is used to transmit to the remote processor the CTS status,
> +as well as the end point address for data transfer.
> +
> +To be compatible with this driver, the remote firmware must create or use its end point associated with "rpmsg-tty-ctrl" service, plus a second endpoint for the data flow.
> +On Linux rpmsg_tty probes, the data endpoint address and the CTS (set to disable)
> +is sent to the remote processor.
> +The remote processor has to respect following rules:
> +- It only transmits data when Linux remote cts is enable, otherwise message
> + could be lost.
> +- It can pause/resume reception by sending a control message (rely on CTS state).
> +
> +Control message structure:
> +struct rpmsg_tty_ctrl {
> + u8 cts; /* remote reception status */
> + u16 d_ept_addr; /* data endpoint address */
> +};
Correct me if I'm wrong, but I think this structure should be packed,
shouldn't it ?
It's working ok on the STM32MP127, between M4 and A7, but the alignment
may be not the same on another architecture ?



> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index c7623f99ac0f..1046bf4aa709 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -454,6 +454,15 @@ config VCC
> help
> Support for Sun logical domain consoles.
>
> +config RPMSG_TTY
> + tristate "RPMSG tty driver"
> + depends on RPMSG
> + help
> + Say y here to export rpmsg endpoints as tty devices, usually found
> + in /dev/ttyRPMSGx.
> + This makes it possible for user-space programs to send and receive
> + rpmsg messages as a standard tty protocol.
> +
> config LDISC_AUTOLOAD
> bool "Automatically load TTY Line Disciplines"
> default y
> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
> index 020b1cd9294f..c2465e7ebc2a 100644
> --- a/drivers/tty/Makefile
> +++ b/drivers/tty/Makefile
> @@ -34,5 +34,6 @@ obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o
> obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o
> obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
> obj-$(CONFIG_VCC) += vcc.o
> +obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o
>
> obj-y += ipwireless/
> diff --git a/drivers/tty/rpmsg_tty.c b/drivers/tty/rpmsg_tty.c
> new file mode 100644
> index 000000000000..3e4d0e1a6663
> --- /dev/null
> +++ b/drivers/tty/rpmsg_tty.c
> @@ -0,0 +1,418 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) STMicroelectronics 2019 - All Rights Reserved
> + * Authors: Arnaud Pouliquen <arnaud.pouliquen@st.com> for STMicroelectronics.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/rpmsg.h>
> +#include <linux/slab.h>
> +#include <linux/tty.h>
> +#include <linux/tty_flip.h>
> +
> +#define MAX_TTY_RPMSG 32
> +
> +#define TTY_CH_NAME_RAW "rpmsg-tty-raw"
> +#define TTY_CH_NAME_WITH_CTS "rpmsg-tty-ctrl"
> +
> +static DEFINE_IDR(tty_idr); /* tty instance id */
> +static DEFINE_MUTEX(idr_lock); /* protects tty_idr */
> +
> +static struct tty_driver *rpmsg_tty_driver;
> +
> +struct rpmsg_tty_ctrl {
> + u8 cts; /* remote reception status */
> + u16 d_ept_addr; /* data endpoint address */
> +};
> +
> +struct rpmsg_tty_port {
> + struct tty_port port; /* TTY port data */
> + int id; /* TTY rpmsg index */
> + bool cts; /* remote reception status */
> + struct rpmsg_device *rpdev; /* rpmsg device */
> + struct rpmsg_endpoint *cs_ept; /* channel control endpoint */
> + struct rpmsg_endpoint *d_ept; /* data endpoint */
> + u32 data_dst; /* data destination endpoint address */
> +};
> +
> +typedef void (*rpmsg_tty_rx_cb_t)(struct rpmsg_device *, void *, int, void *,
> + u32);
> +
> +static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len,
> + void *priv, u32 src)
> +{
> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
> + int copied;
> +
> + if (src == cport->data_dst) {
> + /* data message */
> + if (!len)
> + return -EINVAL;
> + /* data message */
> + copied = tty_insert_flip_string_fixed_flag(&cport->port, data,
> + TTY_NORMAL, len);
> + if (copied != len)
> + dev_dbg(&rpdev->dev, "trunc buffer: available space is %d\n",
> + copied);
> + tty_flip_buffer_push(&cport->port);
> + } else {
> + /* control message */
> + struct rpmsg_tty_ctrl *msg = data;
> +
> + if (len != sizeof(*msg))
> + return -EINVAL;
> +
> + cport->data_dst = msg->d_ept_addr;
> +
> + /* Update remote cts state */
> + cport->cts = msg->cts ? 1 : 0;
> +
> + if (cport->cts)
> + tty_port_tty_wakeup(&cport->port);
> + }
> +
> + return 0;
> +}
> +
> +static void rpmsg_tty_send_term_ready(struct tty_struct *tty, u8 state)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> + struct rpmsg_tty_ctrl m_ctrl;
> + int ret;
> +
> + m_ctrl.cts = state;
> + m_ctrl.d_ept_addr = cport->d_ept->addr;
> +
> + ret = rpmsg_trysend(cport->cs_ept, &m_ctrl, sizeof(m_ctrl));
> + if (ret < 0)
> + dev_dbg(tty->dev, "cannot send control (%d)\n", ret);
> +};
> +
> +static void rpmsg_tty_throttle(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> +
> + /* Disable remote transmission */
> + if (cport->cs_ept)
> + rpmsg_tty_send_term_ready(tty, 0);
> +};
> +
> +static void rpmsg_tty_unthrottle(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> +
> + /* Enable remote transmission */
> + if (cport->cs_ept)
> + rpmsg_tty_send_term_ready(tty, 1);
> +};
> +
> +static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
> +
> + if (!cport) {
> + dev_err(tty->dev, "cannot get cport\n");
> + return -ENODEV;
> + }
> +
> + tty->driver_data = cport;
> +
> + return tty_port_install(&cport->port, driver, tty);
> +}
> +
> +static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
> +{
> + return tty_port_open(tty->port, tty, filp);
> +}
> +
> +static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
> +{
> + return tty_port_close(tty->port, tty, filp);
> +}
> +
> +static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> + struct rpmsg_device *rpdev;
> + int msg_max_size, msg_size;
> + int ret;
> + u8 *tmpbuf;
> +
> + /* If cts not set, the message is not sent*/
> + if (!cport->cts)
> + return 0;
> +
> + rpdev = cport->rpdev;
> +
> + dev_dbg(&rpdev->dev, "%s: send msg from tty->index = %d, len = %d\n",
> + __func__, tty->index, len);
> +
> + msg_max_size = rpmsg_get_mtu(rpdev->ept);
> +
> + msg_size = min(len, msg_max_size);
> + tmpbuf = kzalloc(msg_size, GFP_KERNEL);
> + if (!tmpbuf)
> + return -ENOMEM;
> +
> + memcpy(tmpbuf, buf, msg_size);
> +
> + /*
> + * Try to send the message to remote processor, if failed return 0 as
> + * no data sent
> + */
> + ret = rpmsg_trysendto(cport->d_ept, tmpbuf, msg_size, cport->data_dst);
> + kfree(tmpbuf);
> + if (ret) {
> + dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
> + return 0;
> + }
> +
> + return msg_size;
> +}
> +
> +static int rpmsg_tty_write_room(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> +
> + return cport->cts ? rpmsg_get_mtu(cport->rpdev->ept) : 0;
> +}
> +
> +static const struct tty_operations rpmsg_tty_ops = {
> + .install = rpmsg_tty_install,
> + .open = rpmsg_tty_open,
> + .close = rpmsg_tty_close,
> + .write = rpmsg_tty_write,
> + .write_room = rpmsg_tty_write_room,
> + .throttle = rpmsg_tty_throttle,
> + .unthrottle = rpmsg_tty_unthrottle,
> +};
> +
> +static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
> +{
> + struct rpmsg_tty_port *cport;
> +
> + cport = kzalloc(sizeof(*cport), GFP_KERNEL);
> + if (!cport)
> + return ERR_PTR(-ENOMEM);
> +
> + mutex_lock(&idr_lock);
> + cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
> + mutex_unlock(&idr_lock);
> +
> + if (cport->id < 0) {
> + kfree(cport);
> + return ERR_PTR(-ENOSPC);
> + }
> +
> + return cport;
> +}
> +
> +static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport)
> +{
> + mutex_lock(&idr_lock);
> + idr_remove(&tty_idr, cport->id);
> + mutex_unlock(&idr_lock);
> +
> + kfree(cport);
> +}
> +
> +static int rpmsg_tty_port_activate(struct tty_port *p, struct tty_struct *tty)
> +{
> + p->low_latency = (p->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
> +
> + /* Allocate the buffer we use for writing data */
> + return tty_port_alloc_xmit_buf(p);
> +}
> +
> +static void rpmsg_tty_port_shutdown(struct tty_port *p)
> +{
> + /* Free the write buffer */
> + tty_port_free_xmit_buf(p);
> +}
> +
> +static void rpmsg_tty_dtr_rts(struct tty_port *port, int raise)
> +{
> + dev_dbg(port->tty->dev, "%s: dtr_rts state %d\n", __func__, raise);
> +
> + if (raise)
> + rpmsg_tty_unthrottle(port->tty);
> + else
> + rpmsg_tty_throttle(port->tty);
> +}
> +
> +static const struct tty_port_operations rpmsg_tty_port_ops = {
> + .activate = rpmsg_tty_port_activate,
> + .shutdown = rpmsg_tty_port_shutdown,
> + .dtr_rts = rpmsg_tty_dtr_rts,
> +};
> +
> +static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
> +{
> + struct rpmsg_tty_port *cport;
> + struct device *dev = &rpdev->dev;
> + struct rpmsg_channel_info chinfo;
> + struct device *tty_dev;
> + int ret;
> +
> + cport = rpmsg_tty_alloc_cport();
> + if (IS_ERR(cport)) {
> + dev_err(dev, "failed to alloc tty port\n");
> + return PTR_ERR(cport);
> + }
> +
> + if (!strncmp(rpdev->id.name, TTY_CH_NAME_WITH_CTS,
> + sizeof(TTY_CH_NAME_WITH_CTS))) {
> + /*
> + * the default endpoint is used for control. Create a second
> + * endpoint for the data that would be exchanges trough control
> + * endpoint. address of the data endpoint will be provided with
> + * the cts state
> + */
> + cport->cs_ept = rpdev->ept;
> + cport->data_dst = RPMSG_ADDR_ANY;
> +
> + strscpy(chinfo.name, TTY_CH_NAME_WITH_CTS, sizeof(chinfo.name));
> + chinfo.src = RPMSG_ADDR_ANY;
> + chinfo.dst = RPMSG_ADDR_ANY;
> +
> + cport->d_ept = rpmsg_create_ept(rpdev, rpmsg_tty_cb, cport,
> + chinfo);
> + if (!cport->d_ept) {
> + dev_err(dev, "failed to create tty control channel\n");
> + ret = -ENOMEM;
> + goto err_r_cport;
> + }
> + dev_dbg(dev, "%s: creating data endpoint with address %#x\n",
> + __func__, cport->d_ept->addr);
> + } else {
> + /*
> + * TTY over rpmsg without CTS management the default endpoint
> + * is use for raw data transmission.
> + */
> + cport->cs_ept = NULL;
> + cport->cts = 1;
> + cport->d_ept = rpdev->ept;
> + cport->data_dst = rpdev->dst;
> + }
> +
> + tty_port_init(&cport->port);
> + cport->port.ops = &rpmsg_tty_port_ops;
> +
> + tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
> + cport->id, dev);
> + if (IS_ERR(tty_dev)) {
> + dev_err(dev, "failed to register tty port\n");
> + ret = PTR_ERR(tty_dev);
> + goto err_destroy;
> + }
> +
> + cport->rpdev = rpdev;
> +
> + dev_set_drvdata(dev, cport);
> +
> + dev_dbg(dev, "new channel: 0x%x -> 0x%x : ttyRPMSG%d\n",
> + rpdev->src, rpdev->dst, cport->id);
> +
> + return 0;
> +
> +err_destroy:
> + tty_port_destroy(&cport->port);
> + if (cport->cs_ept)
> + rpmsg_destroy_ept(cport->d_ept);
> +err_r_cport:
> + rpmsg_tty_release_cport(cport);
> +
> + return ret;
> +}
> +
> +static void rpmsg_tty_remove(struct rpmsg_device *rpdev)
> +{
> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
> +
> + dev_dbg(&rpdev->dev, "removing rpmsg tty device %d\n", cport->id);
> +
> + /* User hang up to release the tty */
> + if (tty_port_initialized(&cport->port))
> + tty_port_tty_hangup(&cport->port, false);
> +
> + tty_unregister_device(rpmsg_tty_driver, cport->id);
> +
> + tty_port_destroy(&cport->port);
> + if (cport->cs_ept)
> + rpmsg_destroy_ept(cport->d_ept);
> + rpmsg_tty_release_cport(cport);
> +}
> +
> +static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = {
> + { .name = TTY_CH_NAME_RAW },
> + { .name = TTY_CH_NAME_WITH_CTS},
> + { },
> +};
> +MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table);
> +
> +static struct rpmsg_driver rpmsg_tty_rpmsg_drv = {
> + .drv.name = KBUILD_MODNAME,
> + .id_table = rpmsg_driver_tty_id_table,
> + .probe = rpmsg_tty_probe,
> + .callback = rpmsg_tty_cb,
> + .remove = rpmsg_tty_remove,
> +};
> +
> +static int __init rpmsg_tty_init(void)
> +{
> + int err;
> +
> + rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW |
> + TTY_DRIVER_DYNAMIC_DEV);
> + if (IS_ERR(rpmsg_tty_driver))
> + return PTR_ERR(rpmsg_tty_driver);
> +
> + rpmsg_tty_driver->driver_name = "rpmsg_tty";
> + rpmsg_tty_driver->name = "ttyRPMSG";
> + rpmsg_tty_driver->major = 0;
> + rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE;
> +
> + /* Disable unused mode by default */
> + rpmsg_tty_driver->init_termios = tty_std_termios;
> + rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON);
> + rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR);
> +
> + tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops);
> +
> + err = tty_register_driver(rpmsg_tty_driver);
> + if (err < 0) {
> + pr_err("Couldn't install rpmsg tty driver: err %d\n", err);
> + goto error_put;
> + }
> +
> + err = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
> + if (err < 0) {
> + pr_err("Couldn't register rpmsg tty driver: err %d\n", err);
> + goto error_unregister;
> + }
> +
> + return 0;
> +
> +error_unregister:
> + tty_unregister_driver(rpmsg_tty_driver);
> +
> +error_put:
> + put_tty_driver(rpmsg_tty_driver);
> +
> + return err;
> +}
> +
> +static void __exit rpmsg_tty_exit(void)
> +{
> + unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv);
> + tty_unregister_driver(rpmsg_tty_driver);
> + put_tty_driver(rpmsg_tty_driver);
> + idr_destroy(&tty_idr);
> +}
> +
> +module_init(rpmsg_tty_init);
> +module_exit(rpmsg_tty_exit);
> +
> +MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@st.com>");
> +MODULE_DESCRIPTION("remote processor messaging tty driver");
> +MODULE_LICENSE("GPL v2");
>

Best regards,
Richard

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